1. Field
The present invention relates generally to wireless power, and more specifically, to systems, device, and methods related to sensing and controlling a resonance condition of a wireless power system.
2. Background
Approaches are being developed that use over the air power transmission between a transmitter and the device to be charged. These generally fall into two categories. One is based on the coupling of plane wave radiation (also called far-field radiation) between a transmit antenna and receive antenna on the device to be charged which collects the radiated power and rectifies it for charging the battery. Antennas are generally of resonant length in order to improve the coupling efficiency. This approach suffers from the fact that the power coupling falls off quickly with distance between the antennas. So charging over reasonable distances (e.g., >1-2 m) becomes difficult. Additionally, since the system radiates plane waves, unintentional radiation can interfere with other systems if not properly controlled through filtering.
Other approaches are based on inductive coupling between a transmit antenna embedded, for example, in a “charging” mat or surface and a receive antenna plus rectifying circuit embedded in the host device to be charged. This approach has the disadvantage that the spacing between transmit and receive antennas must be very close (e.g. mms). Though this approach does have the capability to simultaneously charge multiple devices in the same area, this area is typically small, hence the user must locate the devices to a specific area.
As will be appreciated by a person having ordinary skill in the art, the presence of metal objects and/or the presence of a different number of receivers proximate a transmitter may detune the transmitter. A wireless power system having a transmitter and a receiver that are not in a resonant match, may suffer from poor efficiency, which may generate thermal issues and may increase required charging times.
A need exists for methods, systems, and devices to enhance wireless power transfer. More specifically, a need exists for methods, systems, and devices for enabling a transmitter and a receiver within wireless power system to remain in resonant match.